Enhancement of the fluorescence properties of double stranded DNA templated copper nanoparticles

The weak fluorescence emission from dsDNA templated copper nanoparticles necessitates the use of high-end detectors like photomultiplier tubes for their detection. This sets limitations on their applicability to in-situ analyte detection and point-of-care applications which utilize comparatively low cost and less sensitive detectors. In this article, a technique to improve the fluorescence properties of copper nanoparticles templated on dsDNA is reported. The fluorescence enhancement is achieved by introducing a modification in the conventional synthesis technique by using a combination of sodium ascorbate and Taq buffer. When compared to the existing methods, the proposed method achieves 11 times higher fluorescence signal intensity from the dsDNA templated copper nanoparticles and 4 times faster attainment of maximum fluorescence signal. The effect of the ionic strength of the individual constituent components of Taq buffer on the fluorescence emission from the copper nanoparticles is also studied here. The utility of this enhancement strategy for analyte measurement is demonstrated with the example of melamine detection from milk samples. A linear relationship was observed between the fluorescence intensity from the copper nanoparticles and the concentration of melamine in the range from 0.5 ppm to 100 ppm (R² = 0.9919), with a limit of detection of 0.1 ppm. The reported fluorescence enhancement technique also results in 2.95 times improved sensitivity of detection when compared to the conventional technique.